As car intelligence is accelerating, Rohm builds a high wall for safety

【Introduction】

A new round of global technological and industrial revolution is quietly approaching, and electrification, networking, intelligence, and sharing have become the development trend and trend of the automotive industry. Driven by the new four modernizations of automobiles, the automotive electronic and electrical architecture has gradually evolved from the original distributed to cross-domain centralized and vehicle-centralized, the automotive electronic software architecture has been continuously upgraded, and the software and hardware have been layered and decoupled. The era of software-defined cars is coming. The intelligentization of automobiles has accelerated, China's new energy vehicle market is improving, the ADAS function installation rate is constantly rising, L2 is becoming standard, and L3 has begun mass production.

With the trend of intelligent vehicles, functional safety has become the focus of the industry

With the advancement of automobile intelligence and the rapid innovation of autonomous driving technology, safety has become the focus of the industry. There are two types of safety, one is intrinsic safety and the other is functional safety. Intrinsic safety is a method of ensuring safety by eliminating the causes of danger; while functional safety is a method of ensuring safety by reducing risks to an acceptable level through functional efforts. Intrinsic safety can ensure absolute safety, but the cost is often high; in contrast, the cost of functional safety is lower, but the design must take into account how to ensure safety when the additional functions fail.

Figure | Ideas of intrinsic safety and functional safety

For example, at the intersection of railway and road, if the railway and road are separated by building an overpass to physically avoid the collision between trains and cars, this is an intrinsically safe idea. However, if an alarm and a guardrail are set at the intersection of the road and the railway, and a sensor is installed on the railway, when the sensor detects that the train is approaching, the alarm sounds and the guardrail is lowered. When another sensor detects that the train has passed, the alarm stops and the guardrail is raised. Although the road and the railway are still physically intersecting, the risk of collision between cars and trains can be reduced to an acceptable level by setting up a railway crossing. This is the idea of ​​functional safety. Of course, in this case, if the sensor is damaged, the alarm and guardrail will not work when the train approaches, which is a "dangerous" state. Therefore, it is necessary to add sensor self-diagnosis or dual sensor redundant design to ensure that even if the sensor is damaged, it will not cause a dangerous state. This is the idea of ​​Fail Safe.

It can be seen that functional safety is actually a design based on the idea that "people make mistakes" and "things get damaged", and functional safety usually takes into account both "systemic failures" and "random failures" to ensure that there are no systematic bugs and that random failures do not cause harm to people. In China, ISO 26262 (functional safety) has been included in the recommended national standard, and the first Chinese translation of ISO 26262, GB/T 34590, has been implemented since May 2018.

Of course, this requirement is not limited to the automotive field. Many industrial scenarios also have very high safety requirements. In order to build a safer system, it is necessary to consider how to ensure safety when problems occur during the device development process, which means that fault safety and functional safety are throughout the entire device development process.

Reset ICs protect automotive and industrial equipment

When talking about the demand for equipment safety in automotive and industrial application scenarios, we have to mention the importance of monitoring the system power supply voltage. The reset IC is one of the indispensable products in the voltage monitoring circuit. It has been widely used in various automotive and industrial equipment applications that require voltage monitoring of electronic circuits, such as EV/HEV inverters, engine control units, ADAS, car navigation systems, car air conditioners, FA equipment, metering instruments, servo systems, various sensor systems, etc.

In response to this market demand, Rohm has launched more than 1,000 reset ICs . In 2021, it set an annual shipment record of 250 million units in a wide range of applications in the low voltage range. Recently, Rohm has also developed a high-precision, ultra-low power window-type reset IC " BD48HW0G-C " that supports 40V voltage .

Figure | Reset IC operation example

So, what is a reset IC? A reset IC is a switch IC that can be used for voltage monitoring in electronic circuits. When it detects that the monitored voltage exceeds the threshold, it changes the output to achieve the effect of the reset operation. Therefore, it has the function of ensuring system safety by cooperating with the microcontroller. It is like a water level alarm in a river. When the river water overflows the highest warning line or falls below the lowest warning line, the alarm will sound and trigger the release or storage of water. The water level sensor here is like the reset IC in the circuit, and the effect is the same.

What is special about Rohm's new reset IC "BD48HW0G-C"?

Why are there so many types of reset ICs? What are the features or advantages of the latest reset IC "BD48HW0G-C" launched by Rohm? Due to different application scenarios, the system circuit has different requirements for reset IC accuracy, power consumption, operating voltage, functional safety, monitoring voltage range, undervoltage/overvoltage detection, etc., so different reset ICs need to be developed to match the corresponding market needs.

Products marked with this mark are equipped with Nano Energy™ ultra-low quiescent current technology.

* FS supportive: Indicates that this is an IC developed for the automotive field and supports safety analysis related to functional safety.

Figure | Rohm's window reset IC product lineup

Rohm's latest reset IC "BD48HW0G-C" is a window-type reset IC that supports 40V voltage. Due to the use of high-voltage BiCDMOS process and the integration of Rohm's analog design technology, the BD48HW0G-C has a wide operating voltage range of 1.8V to 40V. Regarding the window-type design, since the BD48HW0G-C is equipped with two independent reference voltage circuits, the detection voltages on the High and Low sides can be flexibly set, and the detection output can be reset independently. In terms of detection accuracy, the BD48HW0G-C can achieve the industry's advanced ±0.75% voltage detection accuracy within the temperature range of -40℃-+125℃, which is higher than the industry standard product's accuracy of ±2.2%. In terms of power consumption, the quiescent current of the BD48HW0G-C is only 500nA, which is only 1/16 of the ordinary window-type reset IC with an operating voltage of more than 24V, which allows engineers to design circuits without worrying about the increase in power consumption caused by the reset circuit.

Figure | High-precision reset ICs over the full operating temperature range make system design easier

Why do we need to emphasize stable high-precision characteristics within the full operating temperature range in the automotive and industrial fields? We know that if there is only a value deviation problem at 25°C, it can be easily achieved by adjusting it through fixed compensation. However, in automotive and industrial applications, the ambient temperature and the heating and heat dissipation of the fuselage itself vary greatly. The power supply voltage and reset detection voltage will fluctuate due to the influence of temperature. This deviation under the influence of temperature is very difficult to correct. Therefore, for automotive and industrial environments, choosing a stable high-precision reset IC within the full operating temperature range is easier for system design, thereby reducing the design burden of customers. In addition, in automotive and industrial environments, the environmental noise is usually large. When external noise invades, if the voltage detection accuracy is poor, it is easy to cause malfunction. Therefore, in order to avoid or reduce the influence of external noise and improve the reliability of system operation, a high-precision reset IC is a better choice.

It is worth mentioning that ROHM has started to build the ISO 26262 process since 2015, and obtained the ISO 26262 process certification from German third-party certification agency TÜV Rheinland in March 2018, about two and a half years later. Because of its deep understanding of ISO 26262 specifications and application circuits, ROHM has developed a reset IC that supports a wide voltage range from low to high and detects voltage anomalies with high accuracy for automotive and industrial power supplies that require functional safety.

The Secret to Ultra-Low Power Consumption in Analog Power Devices: Nano Energy™

As mentioned earlier, the quiescent current of BD48HW0G-C is only 500nA, which is only 1/16 of the ordinary window-type reset IC with an operating voltage of more than 24V. How is such ultra-low power consumption achieved?

In fact, Rohm adopts the IDM model. Under this vertically integrated production system, Rohm has deeper experience accumulation and stronger analog technology advantages in the three aspects of "circuit design", "layout" and "process". Based on this, Rohm has developed a groundbreaking technology "Nano Energy™" that completely reduces current consumption under ultra-light load conditions. Using this technology, the static current under no load can be as low as nanoamperes (nA), which can not only extend the driving time of battery-powered IoT devices and mobile devices, but also help in-vehicle and industrial equipment that do not want to increase power consumption to work efficiently.